Unless otherwise indicated herein, the description in this section is not prior art to the claims in this application and is not admitted to be prior art by inclusion in this section.
An image forming apparatus of an electrophotographic system performs a development process on an electrostatic latent image formed on a surface of an image carrier, such as a photoreceptor drum and an intermediate transfer belt, by supplying toner from a developer unit. The toner is housed in a toner container. When a toner density in the developer unit decreases, the toner container is driven by a motor for toner replenishment, and while the toner inside the toner container is stirred by a stir paddle, the toner is replenished to the developer unit by a transport screw.
In a color image forming apparatus, four colors of toner are used, and there are also four toner containers in total for respective colors. Therefore, when one motor for toner replenishment is mounted to the toner container of the respective colors, four motors are necessary and become a factor of cost increase. There is provided a conventional technique that locates a solenoid and a clutch mechanism in a toner replenishment apparatus. The toner replenishment apparatus can replenish toner to two or four developer units with one motor by switching of the clutch by ON/OFF control of the solenoid.